Field sterilizer



Feb. 14, 1967 B D P|| E 3,304,149

FIELD STERILIZER n Filed June 24, 1963 4 Sheets-Sheet 2 INVENTOR. BENJAM/A/ D. DA/ E AfToQA/Ey Feb. 14, 1967 B. D. PILE FIELD STERILIZER 4 Sheets-Sheet 3 Filed June 24, 1963 INVENTOR.

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FIELD STERILIZER Filed June 24, 1963 4 Sheets-Sheet 4 INVENTOR. BENJAMIN D. p/Le WW@ M A TToQ/VE y United States Patent 3,304,149 FHELD SERELIZER Benjamin D. Pile, Bayside, N.Y., assigner to the United States of America as represented by the Secretary of the Army Filed June 24, 1963, Ser. No. 290,265

3 Claims. (Cl. 21-93) The invention described herein may be manufactured and used by or for the Government for governmental purposes without p-ayment to me of any royalty.

The present invention relates to the field of apparatus for sterilizing surgical dressings, instruments and the like.

Two general types of steam stcrilizers or autoclaves are presently used for sterilizing surgical dressings, surgical and dental instruments and the like. The double shell type sterilizer typically comprises two concentric cylinders, the inner shell serving as the sterilizing chamber and the space between shells functioning as the steam generator. For the sterilizing operation steam produced in the generating space is admitted to the inner chamber. After the sterilizing period the steam is exhausted from that chamber and the dressings or instruments are left therein to be dried by heat transmitted through the sterilizing chamber walls. The typical double shell sterilizer is expensive to manufacture and heavy.

The other type steam sterilizer in general use is the single shell type. In the single shell sterilizer a quantity of water is introduced into the sterilizing chamber itself, heat is applied directly to the sterilizing chamber and the steam is `generated therein. After the sterilizing period is completed, steam is exhausted from the chamber and the heating of the chamber continues until the contents of the sterilizer are dried. Burning or scorching of dressings is a common occurrence with single shell sterilizers particularly when the source of heat is a direct flame.

In addition to the deciencies just described, most of the steam sterilizers or autoclaves in common use have other characteristics which limit their value to military or other medical organizations operating in the field. The complicated design and special features of conventional sterilizers which may be desirable at 4permanent medical installations may cause operating and maintenance problems in the field.

Accordingly, an object of this invention is to provide a simple efficient lightwei-ght sterilizer which can be economically manufactured and which is suitable for use in the field.

Another object of this invention is to provide a steam sterilizer having a sterilizer chamber separate from the steam -generator in which the steam generator functions as a heat sink to prevent overheating of the sterilizer chamber during the drying cycle.

Another object of the invention is to provide a steam sterilizer having a carrying or shipping case which when opened serves as a stand to support the sterilizer in an elevated position.

These and other objects and advantages of the invention will be made clear in the drawings and in the description which follows.

In the drawings:

FIG. 1 is a side elevation with parts broken away of the field sterilizer in its operating position;

FIG. 2 is a rear elevation of the field sterilizer in its operating position.

FIG. 3 is a partial front elevation of the eld sterilizer in its operating position;

FIG. 4 is an exploded perspective view showing most of the principal elements of the eld sterilizer;

FIG. 5 is a perspective view partly in section of a part of the sterilizer chamber;

FIG. 6 is a diagrammatic representation of the sterilizers plumbing;

FIG. 7 shows the sterilizer in its closed or carrying condition;

FIG. 8 is a perspective view of the frame of the carrying case; and

FIG. 9 is an enlarged perspective view of the hinge used with the covers.

The eld sterilizer comprises four principal components as most clearly appears in FIG. 4; a chamber unit 1, a fume hood 2, a carrying case 3 and a burner unit 4. The chamber unit 1 is mounted in the fume hood 2 which Iis .in turn mounted in the carrying case 3. The burner unit 4 is attached to the carrying case when the sterilizer is operated. When the sterilizer is transported, the burner unit 4 may be carried within the chamber unit 1. Aluminum or other lightweight metal is used to the maximum extent practicable for the various components of the sterilizer.

The chamber unit 1 comprises a generally cylindrical sterilizer chamber 5 and a steam generator chamber 6. The steam generator chamber which is fabricated as a section of a cylinder closed at both ends is seam welded along its upper edges to the :bottom surfaceI of sterilizer chamber 5. Thus a portion of the bottom surface of the sterilizer chamber serves as the top surface of -generator chamber 6. A visual type water gauge 7 is provided in the rear end wall 8 of the generator chamber 6. A rectangular cleanout hole 9 with a removable cover is provided in front wall 11 of the generator chamber. A water drain nipple 12 closed by a removable threaded plug is welded into the bottom of generator chamber 6.

Sterilizer cham-ber 5 is closed by curved end wall 13 welded to the cylindrical body portion 14 of the sterilizer chamber. A generally circular door flange 15 of cast aluminum alloy is welded to the front edge of cylindrical body portion 14. Integral-ly formed with the ange and extending outward from its periphery are a pair of door posts 16, a pair of guide projections 17 having holes 18 drilled therethrough, and a plurality of bifurcated projections 19. Transverse aligned holes are bored through the two legs of each bifurcated `projection 19.

Circular outwardly curved sterilizer door 21 is cast from an aluminum alloy. The door rim face 22 seats against face 23 of .the sterilizer flange when the door is closed. A door gasket, not shown, of the O-ring type received in a circular groove cut into door rim face 22 forms a pressure tight seal between the door and sterilizer flange when the door is closed. One-fourth inch diameter butyl rubber door gasket of 6() durometer hardness is satisfactory.

Sterilizer door 21 is formed with a central boss 26, a plurality of bifurcated projections 27 at its periphery matching projections 19 in sterilizer flange 15 and top and bottom projections 2S matching the guide projections 17 on the sterilizer flange. Curved door arm 29 is attached by screw 3) or other suitable means to central lboss 26 of the door. A bolt 31 which passes through aligned holes in the door posts and a hole in the proximal end oft-he door arm serves as the hinge pin on which sterilizer door 21 pivots. A door handle 32 of heat insulating material is attached to the distal end of door arm 29. Guide pins 33 having conical head portions adapted to be received in holes 18 of guide projections 17 are attached to top and bottom projections 28 of the door.

The locking means byl which the sterilizer door 21 can be brought into and held in tight sealing engagement with sterilizer ange 15 comprises a plurality of toggle bolts 36 and hand nuts 37. Each toggle bolt 36 is pivotally mounted on a toggle bolt pin between the arms of one of the bifurcated projections 19. The distal end of each toggle bolt is threaded and receives a hand nut 37. The toggle bolts may be swung outward when the door is to be opened. When the sterilizer door has been closed and is to be locked, the toggle bolts may be swung forward so that their shafts lie between the arms of the bifurcated projections 27 on the door, The operator may then manually tighten hand nuts 37 thereby locking the door in sealing engagement with the sterilizer tlange. The operator grips the insulated door handle to open and close the door; when the door is being closed guide pins 33 are received in guide holes 18 thus insuring proper alignment between the door and the sterilizer ange.

A horizontal rectangular perforated shelf plate 39 is attached by intermittent welding at its edges to the interior wall of sterilizer chamber along the lines formed yby the intersection of sterilizer chamber 5 and generator chamber 6. Thus, shelf plate 39 functions not only as a shelf to hold material being sterilized but also as a structural member when the generator chamber is filled with steam under pressure and the sterilizer chamber is at atmospheric Ipressure. A generally circular flanged steam diffuser plate 40 is ailxed to the back edge of shelf plate 39. When steam is admitted to the sterilizer chamber, in a manner to be described hereafter, it is deflected toward the walls of the sterilizer chamber by steam dif* fuser plate 40.

The chamber unit 1 may lbe chromic acid anodized both externally and internally to prevent corrosion and pitting, The chamber unit 1 is mounted in the fume hood 2 which supports the chamber unit and serves as a flue to channel the products of combustion from the burner past the cylindrical -body portion 1 4 of the steri* lizer chamber. The fume hood 2 which may be fabricated of sheet aluminum comprises identical front and rear walls 41 and 42, respectively. End opening 43 in the shape of two overlapping circles is cut through the front wall 41 and a similar opening 44 is cut through the rear wall 42. Openings 43 and 44 correspond in size and shape to the cross section of the chamber unit. The front and rear walls of the fume hood are welded at their top and side edges to a continuous side wall portion 45. The upper parts of the side wall portion curves to form half of a cylinder. ured along side wall portion 45 is slightly less than the distance between front wall 11 of steam generator 6 and water drain nipple 12 in the steam generator. Thus when chamber unit 1 is placed within fume hood 2, the steam generator 6 may be supported by both the front and rear walls of the fume hood while nipple 12 falls just outside the fume hood.

Fume hood 2 is open at its bottom except that the front and rear walls and the side wall portion are bent inwardly at their bottoms at right angles to form a lip 46 whose purpose will appear presently. To facilitate installation and repair a transverse cut 47 may be made -through the bottom of the front and rear walls and their adjacent lips 46. With such cuts the bottom portions of the front and rear walls may be pulled apart expanding the diameter of the openings 43 and 44. Hood splices, not shown, formed from lengths of aluminum angle may be used -to removably span transverse cuts 47, When they are fastened to lips 46 on both sides of cuts 47 by bolts or other suitable means the fume hood 2 is a unitary structure. Circular opening 49 is made through the top of the fume hood.

A flame deector 50 consisting of two longitudinal members S1 having front and rear lip portions 52 and a pair of spaced lateral plates 53 is mounted within fume hood 2 by bolts passing through front and rear walls of the fume hood and the adjacent lip portions 52 of the ame deectors longitudinal members. The lateral plates 53 which are curved at their centers to correspond with The length of the fume hood meas-v the radius of steam generator 6 restrict the ame from the burner to a relatively small area of the steam generator and result in more eicient heating. The lateral plates also form a saddle on which the bottom of the steam generator rests.

The carrying case 3 in which the fume hood and charnber unit subassembly is mounted comprises a rectangular case body 55 open at both ends and at its bottom. The framework of case body 55 and case end covers 56 appears most clearly in FIG. 8. It may be fabricated of aluminum tube members 57 and bar stock members 58. A pair of spaced aluminum angles 59 form the longitudinal members in the bottom of case body 55. A number of rectangular aluminum tabs 60 are welded to the framework providing additional surfaces to which the outer skin may be spot welded. A pair of burner support members 61 formed of Hat bar stock are transversely attached to two longitudinal bar stock members on one side of case body 55.

Cover aligning plugs 62 having rounded heads are fixed within tube members 57a at the top sides of case end covers 56. The cover aligning plugs project beyond the end of tube members 57a and are adapted to be received within the ends of tube members 57b when the covers are closed. Thus cover aligning plugs 62 function to align the end covers and case body when the carrying case is closed. The top and sides of case body 55 are covered with sheet aluminum which may have spaced apart corrugations. The exterior ends, top, bottom and sides of end covers 56 are likewise covered with sheet aluminum. The sheet aluminum for both the case body and end covers is welded to the several tube, bar stock and angle members which comprise the frame and to the rectangular tabs 60.

The details of a suitable hinge for attaching the end covers 56 to the case body 55 are shown in FIG. 9. Each hinge 65 is in the shape of a generally rectangular block having two parallel passages drilled therethrough. The hinge is made in two halves 65a and 6512 and is assembled with tube member 57C of the case body passing through one hinge passage while tube member 57d of an end cover passes through the other hinge passage. The hinge halves 65a and 6517 are held together by hinge screw 66 which passes through tube member 57d. Each hinge 65, therefore, is freely rotatable about tube member 57C. Each cover 56 is capable of 180 rotation between a closed position and an open position in which case body 55 may be supported upon the upstanding end cover 56.

Rectangular openings 67 are made in the top and end vwalls adjacent tube member 57e in each end cover 56.

These openings make it possible for personnel to grasp tube members 57e when lifting the sterilizer. They also cooperate in a manner to be explained hereinafter with a locking strap in locking the carrying case in its closed and in its operating positions.

A circular opening 68 is cut in the top of case body 55 directly over the position which circular opening 49 of fume hood 2 will occupy when the fume hood is installed in the carrying case. A pair of keyhole shaped burner mounting slots 69 are cut through one of the sides of case body 55 and through the underlying burner support members 61'.

The manner in which chamber unit 1, fume hood 2 and flame deector 50 are assembled has already been described. The chamber unit-fume hood subassembly is mounted within case body 55 with the bottom side edges of fume hood 2 received in and supported by angle members 59. The side portions of the fume hoods bottom lip are fastened to angle members 59 by screws or other suitable means. The chamber unit-fume hood subassembly is further secured to case body 55 by transverse retainer member 70 (see FIG. 2). Retainer member 70, which is attached at its ends to the bases of angle members 59, receives water drain nipple 12 in a central opening. A fume chimney 72 comprising a ange 73 and a f rising stem gate type.

cylindrical portion 74 is bolted by its flange to case body 55 with the cylindrical portion 74 depending through circular opening 68. The cylindrical portion 74 of the fume chimney is of larger diameter than opening 49 of the fume hood. Cylindrical portion 74 is of such a length and its bottom edge is so curved that there is a close fit between the bottom edge of cylindrical portion 74 and the top of fume hood 2.

The sterilizer plumbing is diagrammatically illustrated in FIG. 6. It comprises a funnel 75, gate valves 76, 77 and 78, air release valve 79, safety valve 80, pressure gauge 81, temperature gauge 82 and a trap 83. To reduce weight it is desirable that the piping which includes branches 84, 85, 86, 87, 88, and 89 and all fittings be of aluminum. However, to save expense, or for emergency repairs, standard piping or ttings of any material may be used. Valves .76, 77 and 78 have cast aluminum bodies with stainless steel stems and seats. They are of the non- Trap 83 should have an element operating at about 250 Fahrenheit. It should vent air and condensation from sterilizer chamber 5 when that chamber is being filled with steam and should stop venting afterrthev 250 Fahrenheit temperature is reached. The functions of the various fittings will be explained more fully hereafter when the operation of the sterilizer is described.

Any suitable heat source may be used as a burner unit to generate steam in generator chamber 6. In addition to being capable of generating an adequate supply of steam at sterilizing temperatures and pressures, it is desirable that the burner unit lbe lightweight and able to burn leaded gasoline which is often the only fuel readily available during military field operations. The burner unit 4, illustrated, comprises burner frame 90, a fuel tank 91, a burner proper 92 and a pair of burner support brackets 93. Each burner support bracket 93 has a button shaped projection 94 thereon adapted to removably engage one of the keyhole shaped burner mounting slots 69. The burner proper 92 is so located in relation to burner bracket 93 that when the burner unit is attached to case body 55 by means of projections 94 the burner proper 92 is located underneath steam generator 6. It should be apparent that although it is convenient to utilize a burner which can be attached to the case body, it is not essential that the burner unit be so attached. For example, a burner supported upon a box underneath the open bottom of case body 55 will operated quite satisfactorily.

An adjustable locking strap 95 having hook elements 96 at each end is also provided. Locking strap 95 is used to lock the end covers 56 in their closed condition when the sterilizer is transported in the manner shown in FIG. 7, the hook elements engaging tube member 57C of each end cover. Adjustable strap 9.5 is similarly used to interconnect and secure end covers 56 in their open position as shown in FIG. 1.

In order to use the sterilizer it is first set up in the operating position illustrated in FIGS. l-3. The dressings or other material to be sterilized are placed on shelf 39. The sterilizer door 21 is closed and secured by swinging toggle bolts 36 forward and tightening hand nuts 37. Water is added to steam generator chamber 6 until the liquid level reaches to top of Water gauge 7. Air release valve 79 which may be of any conventional design is opened while the water is added to allow air to escape from the generator chamber. Water ll valve 76 is open and steam inlet valve 77 is closed during the filling operation. Water poured into funnel 75 passes through branches 84 and 85 to the generator chamber 6. After water has been added water ll valve 76 and air release 79 are closed.

After water is added to the steam generator the generator should be heated by burner 92 until pressure gauge `81 indicates that the pressure within the steam generator is about 25 pounds per square inch gauge. Steam inlet valve 77 is opened and steam exhaust valve 78 is checked to make sure that it is closed. Steam is then able to flow from the steam generator 6 through branches 85, 86 and 87 into the sterilizer chamber 5. Air and condensate will be forced out of sterilizer chamber 5 through branch 89 and will escape through trap 83. When pressure gauge 81 again registers 16 to 17 pounds and the temperature as shown on temperature gauge 82 registers 250civ to 254 Fahrenheit the sterilization period begins. These pressure and temperature ranges may be maintained during the sterilizing process by regulating the heat applied to the steam generator. The pressure release or safety valve 80 should be set to open at approximately 25 pounds pressure.

At the end of the sterilizing period steam inlet valve 77 should be closed and steam exhaust valve 78 opened permitting steam to escape from the sterilizer chamber through branches 87 and 88 to the atmosphere. When the ow of exhausting steam becomes negligible, sterilizer door 21 should be opened slightly. The drying period then commences. The burner continues to apply heat to both the steam generator and to the exterior of the sterilizer chamber sides. Burner operation should be regulated during the drying period so that the pressure shown on pressure gauge 81 does not exceed 24 pounds. When the drying cycle is completed the load is removed from the sterilizer chamber and the burner is shut off or allowed to continue burning depending on whether additional material is to be sterilized or not. When the burner is nally shut down the pressure wtihin the steam generator should be allowed to drop to zero by cooling. When pressure gauge 81 registers zero, air release valve 79 should be reopened to prevent any vacuum from forming within the steam generator chamber 6. The generator chamber 6 serves as a buffer or heat sink which prevents scorching of dressings or other material subject to damage by overheating.

A prototype field sterilizer of the present invention has been constructed largely of aluminum alloy materials. The sterilizing chamber is 16 inches in diameter and 24 inches in length and the steam generator has a capacity of approximately 3 gallons of water. A burner unit weighing only 7 pounds with a tank capacity of approximately 1 gallon of gasoline was used. The burner which is of the self-generating type has a 30,000 B.t.u. rating and a fuel jet orifice approximately 1&2 of an inch in diameter. With an orifice this large the burner is less likely to become clogged and leaded gasoline can be used with satisfactory results.

When closed, the prototype eld sterilizer is 23 inches wide 'by 36 inches long by 271/2 inches high. The weight of the prototype field sterilizer complete with the burner is 125 pounds. The present standard field sterilizer used by the Army Medical Corps which is of comparable capacity occupies a cube of 21.96 cubic feet compared with the 15 cubic feet occupied by the field sterilizer of the present invention and the standard field sterilizer weighs 480 pounds nearly four times as much as the prototype lof the present invention.

It will be apparent to persons skilled in the art that the chamber unit described herien, although it is ideally suited to and intended for use in combination with a fume hood and carrying case, could be supported in any suitable supporting frame and utilized as a steam sterilizer. It should also be apparent that many of the details of the embodiment described herein may be varied without departing from the principle of the invention.

I claim:

1. A field sterilizer comprising:

(a) a carrying case including a body portion open at opposite ends and at the bottom thereof and having a fume opening in its top surface and a pair of end covers, each cover hingedly attached to said body portion at the bottom edge of one of the open ends, the said end covers being pivotable through an angle of about 180 between their closed positions and their open positions in which they serve as a stand for the sterilizer;

(b) a chamber unit mounted within the body portion of said carrying case including a sterilizer chamber having an access opening at one end and a sealing door for selectively closing said access opening and a steam generator chamber aixed to the bottom surface of said sterilizer chamber;

(c) heating means comprising a burner unit disposed in heat transfer relationship with said steam generator chamber for producing steam therein;

(d) a ue-like fume hood intermediate said chamber unit and said carrying case substantially `encasing the sides and top of said chamber unit and communicating with the opening in the top of the body portion of said carrying case;

(e) means including a valve, interconnecting said generator chamber and said sterilizer chamber, for selec- 20 tively admitting steam from said generator chamber into said sterilizer chamber;

(f) a trap connected to said sterilizer chamber for a1- lowing air and condensate to escape from said sterilizer chamber when steam is admitted thereto; and 2 (g) a valve connected to said sterilizer chamber for selectively permitting steam to escape from said sterilizer chamber.

2. A field sterilizer as described in claim 1 wherein said burner unit is selectively attached to the. body portion of said carrying case with the burner proper `subjacent said steam generator chamber.

3. A eld sterilizer as described in claim 1:

(a) wherein the sterilizer chamber is generally cylindrical in shape and the steam generator chamber is a section of a cylinder, the longitudinal axes of the two chambers being parallel to each other; and

(b) wherein a shelf is disposed Within said sterilizer chamber the sides of said shelf affixed to the inner Wall of the sterilizer chamber adjacent the junctures of the side wall of the sterilizer'chamber with the side Wall of the steam generator chamber.

References Cited by the Examiner UNITED STATES PATENTS 470,966 3/1892 Andro 21-98 698,711 4/1902 Kellogg 21-98 717,448 12/1902 Pease et al. 21--98 791,490 6/1905 Parmentier 21-Ls4 2,112,639 3/1938 Underwood 21-9'8 MORRIS O. WOLK, Prnmry Examiner.

I. ZATARGA, Assistant Examiner. 

1. A FIELD STERILIZER COMPRISING: (A) A CARRYING CASE INCLUDING A BODY PORTION OPEN AT OPPOSITE ENDS AND AT THE BOTTOM THEREOF AND HAVING A FUME OPENING IN ITS TOP SURFACE AND A PAIR OF END COVERS, EACH COVER HINGEDLY ATTACHED TO SAID BODY PORTION AT THE BOTTOM EDGE OF ONE OF THE OPEN ENDS, THE SAID END COVERS BEING PIVOTABLE THROUGH AN ANGLE OF ABOUT 180* BETWEEN THEIR CLOSED POSITIONS AND THEIR OPEN POSITIONS IN WHICH THEY SERVE AS A STAND FOR THE STERILIZER; (B) A CHAMBER UNIT MOUNTED WITHIN THE BODY PORTION OF SAID CARRYING CASE INCLUDING A STERILIZER CHAMBER HAVING AN ACCESS OPENING AT ONE END AND A SEALING DOOR FOR SELECTIVELY CLOSING SAID ACCESS OPENING AND A STEAM GENERATOR CHAMBER AFFIXED TO THE BOTTOM SURFACE OF SAID STERILIZER CHAMBER; (C) HEATING MEANS COMPRISING A BURNER UNIT DISPOSED IN HEAT TRANSFER RELATIONSHIP WITH SAID STEAM GENERATOR CHAMBER FOR PRODUCING STEAM THEREIN; (D) A FLUE-LIKE FUME HOOD INTERMEDIATE SAID CHAMBER UNIT AND SAID CARRYING CASE SUBSTANTIALLY ENCASING THE SIDES AND TOP OF SAID CHAMBER UNIT AND COMMUNICATING WITH THE OPENING IN THE TOP OF THE BODY PORTION OF SAID CARRYING CASE; (E) MEANS INCLUDING A VALVE, INTERCONNECTING SAID GENERATOR CHAMBER AND SAID STERILIZER CHAMBER, FOR SELECTIVELY ADMITTING STEAM FROM SAID GENERATOR CHAMBER INTO SAID STERILIZER CHAMBER; (F) A TRAP CONNECTED TO SAID STERILIZER CHAMBER FOR ALLOWING AIR AND CONDENSATE TO ESCAPE FROM SAID STERILIZER CHAMBER WHEN STEAM IS ADMITTED THERETO; AND (G) A VALE CONNECTED TO SAID STERILIZER CHAMBER FOR SELECTIVELY PERMITTING STEAM TO ESCAPE FROM SAID STERILIZER CHAMBER. 